1. Field of the Invention
The present invention relates to a cross substrate, a method of mounting a semiconductor element, and a semiconductor device, and in particular to a cross substrate which is a mount substrate to which a semiconductor substrate is mounted, and to a method of mounting a semiconductor element to the cross substrate.
2. Description of the Related Art
In a conventional method of manufacturing a semiconductor device in which a semiconductor element is mounted on a mount substrate, as illustrated in FIG. 10, a semiconductor element 82 is disposed on a wiring forming surface 80a of a mount substrate 80 such that a circuit forming surface 82a of the semiconductor element 82 is the upper surface. After the semiconductor element 82 is fixed by an adhesive to the mount substrate 80, a substrate side electrode 84 and an element side electrode 86 are bonded by a metal wire 88 such as a gold wire, and the structure is sealed and packaged by a sealing resin 81 which is insulative.
As illustrated in FIG. 10, the semiconductor device obtained by this method becomes excessively thick by an amount corresponding to the loop height H of the wire 88 and the thickness L of the sealing resin 81 covering the wire 88. In order to overcome this problem, various mounting methods have been proposed.
xe2x80x9cIn one such method, as illustrated in FIG. 11, with the circuit forming surface 82a of the semiconductor element 82 and the wiring forming surface 80a of the mount substrate 80 opposing one another, the substrate side electrodes of the mount substrate 80 and the element side electrodes of the semiconductor element 82 are joined together by solder bumps 85. The space between the circuit forming surface 82a of the semiconductor element 82 and the wiring forming surface 80a of the mount substrate 80 is sealed by the sealing resin 81 which is insulative. As shown in FIG. 11, because no wire is used in a semiconductor device obtained by this method, a semiconductor device having a thinner package can be obtained.xe2x80x9d
In recent years, the demand to shrink products equipped with semiconductor devices has increased even more. However, there are limits to shrinking the dimensions of semiconductor devices. Further, because there are limits to shrinking the mounted volume of semiconductor devices, conventional methods cannot completely satisfy this demand.
Namely, in the case of the structure of the conventional semiconductor device illustrated in FIG. 10 and described above, if the entire length of the wire is increased to a certain extent, there are problems such as the wire may contact the corner portion of the semiconductor element and form a short circuit, or the wire may break resulting in a defective connection, or in the worst case, the wire may be disconnected. Because the length of the wire must be extended to a certain extent, the resin sealing the wire becomes thicker than the wiring substrate, and the semiconductor device package becomes that much thicker. Thus, there are limits to shrinking the overall dimensions of the semiconductor device. Further, load may be applied to the wire during the sealing by the sealing resin, or the wire may contact an adjacent wire and form a short circuit, and there is thus the concern that the wire may be broken.
In the case of the structure illustrated in FIG. 11, because no wires are used, the problems associated with wires can be avoided, and the semiconductor device on the whole can be made thinner than the semiconductor device illustrated in FIG. 10. However, because the solder bumps are provided between the mount substrate and the semiconductor element, the semiconductor device becomes excessively thick by an amount corresponding to the height of the solder bumps.
In view of the aforementioned, an object of the present invention is to provide a cross substrate on which semiconductor elements can be mounted at a high density, a method of mounting a semiconductor element, and a semiconductor device.
The first aspect of the present invention is a cross substrate including at least one resin sealed layer of a cross member, the at least one resin sealed layer of a cross member having warp threads and weft threads, wherein a portion of at least one of the warp threads and weft threads include a plurality of conductive thread-like wire members disposed substantially parallel to one another, with the wire members electrically insulated from one another, and an electrode portion formed at one region of the thread-like wire members.
In the first aspect of the present invention, the cross member forms a wiring portion of the cross substrate at which a semiconductor element is mounted. In order to electrically connect the semiconductor element and the wires, the electrode portions of the semiconductor element are electrically connected to at least one portion of the thread-like wire members which are the wires. Thus, the position at which the semiconductor element is mounted is not limited by the positions at which the electrode portions of the cross member are formed, and the semiconductor element can be mounted relatively freely. Accordingly, semiconductor elements can be mounted at a high density, and the obtained product has a more compact structure than conventional products.
If the thread-like wire members are used, there is no need to provide the electrodes of the semiconductor element at the periphery as in the case of conventional wire bonding. The positions of the electrodes provided at the semiconductor element can be determined freely. Therefore, the number of degrees of freedom in the arranging and designing of the circuit formed on the semiconductor element increases, and the region for the circuit of the semiconductor element can be utilized effectively. Therefore, the semiconductor element is more compact than conventional semiconductor elements, and as a result, the product can be made more compact.
The cross substrate is used not only for the mounting of a semiconductor element to a structure in which a cross member is sealed by sealing resin in advance, but also can be used when the semiconductor element is sealed and mounted at the time the cross members is sealed by sealing resin, as will be explained later.
Namely, the tenth aspect of the present invention is one method of mounting a semiconductor element in which a semiconductor element is mounted to the cross substrate of the first aspect. This method includes the steps of: (a) providing a cross member having at least one layer of warp threads and weft threads, wherein a portion of at least one of the warp threads and weft threads include a plurality of conductive thread-like wire members disposed substantially parallel to one another, with the wire members electrically insulated from one another, and an electrode portion formed at one region of the thread-like wire members; (b) mounting a semiconductor element having an electrode forming surface with a plurality of electrodes thereat, onto the at least one layer of the cross member such that at least one of the plurality of electrodes of the semiconductor element is electrically connected to at least one of the thread-like wires; and (c) sealing the cross member and the electrode forming surface of the semiconductor element with an insulating resin.
As in a second aspect and an eleventh aspect of the present invention, it is preferable that the thread-like wire members have surfaces covered by an insulating material, other than at the electrode portion. In this way, the occurrence of short circuits and the like can be suppressed.
As in a third aspect and a twelfth aspect of the present invention, thread-like wire members can be provided in plural directions by the following structure: the cross substrate further comprises at least one other layer of a cross member, the at least one other cross member having warp threads and weft threads, wherein a portion of at least one of the warp threads and weft threads include a plurality of conductive thread-like wire members disposed substantially parallel to one another, the thread-like wire members of each cross-member being oriented in a direction different from the thread-like wire members in the other cross-member. Therefore, limitations on the positions for mounting the semiconductor element due to the positions at which the electrode portions of the cross members are formed are eliminated, and semiconductor elements can be mounted at an even higher density.
In a fourth aspect and a thirteenth aspect of the present invention, thread-like wire members are used whose surfaces are covered with an insulative material, other than at positions at which the electrodes of the semiconductor element are provided. A portion of both of the warp threads and the weft threads include a plurality of conductive thread-like wire members disposed substantially parallel to one another, with the wire members electrically insulated from one another, and at an intersecting position, at least one wire member of the warp threads crosses at least one wire member of the weft threads, and are electrically connected to one another at the intersecting position.
Namely, portions, other than the electrode positions, of the conductive thread-like wire members are covered by an insulative material. Therefore, the warp threads and the weft threads are formed by conductive thread-like wire members. Even if these thread-like wire members are used as the wires for the cross substrate, the warp thread wires and the weft thread wires do not contact one another and form a short circuit. Further, in the fourth aspect and thirteenth aspect, one of the plurality of conductive thread-like wire members which are provided as the warp threads and one of the plurality of conductive thread-like wire members which are provided as the weft threads are electrically connected at a intersecting position. Thus, the wires can extend in two different directions.
A fifth aspect of the present invention is a cross substrate including: (a) a plurality of conductive members extending in a predetermined first direction; and (b) a plurality of insulating members extending in a second direction intersecting the first direction, and disposed so as to traverse regions between adjacent conductive members.
A ninth aspect of the present invention is a semiconductor device in which a semiconductor element is mounted to the cross substrate of the fifth aspect. Namely, the semiconductor substrate of the ninth aspect includes a semiconductor element having a surface with a plurality of electrodes thereat; a plurality of conductive members which extend in a predetermined first direction with each conductive member electrically connected to a corresponding electrode of the semiconductor element; a plurality of insulative members which extend in a second direction transverse to the first direction, and which are disposed so as to traverse regions between adjacent conductive members; and a sealing resin, the conductive members having surfaces and the conductive members and the electrodes having connected portions, the sealing resin sealing at least the surfaces and connected portions, and leaving at least one portion of the plurality of conductive members exposed.
Namely, the cross substrate of the fifth aspect is formed from a plurality of conductive members and a plurality of insulative members which intersect one another. The cross substrate is well-suited for a case in which the semiconductor element is sealed together with the cross substrate by sealing resin after having been mounted to the cross substrate. Because there is no need to resin-seal the cross substrate itself at the time of manufacturing the cross substrate, the processes for manufacturing the semiconductor device are simplified. Further, in the semiconductor device of the ninth aspect, after the semiconductor element is mounted to the cross substrate of the fifth aspect, the semiconductor element is sealed together with the cross substrate by resin.
In a sixth and a fourteenth aspect of the present invention, the cross substrate forms a casing having an interior with an inner side surface, and a semiconductor element is provided at an inner side surface of an interior of the casing.
Namely, the cross substrate itself, which is a mount substrate and whose core material is the flexible cross member, is sealed by resin. Therefore, the configuration of the cross substrate can be set freely.
For example, sealing by resin is carried out in a state in which the cross member is placed in the casing of an electric product such as a cellular phone or a personal computer or the like. In this way, a cross substrate having the same configuration as the casing can be obtained, and therefore, a casing can be obtained which serves as both a casing and as a cross substrate on which a semiconductor element is mounted. Of course, because the flexible cross member is used as the core material, the cross substrate is relatively flexible even after the resin sealing is carried out. Therefore, the cross substrate can be deformed to a desired configuration by application of an external force such as a bending force.
Namely, the cross substrate, which is a mount substrate at which a semiconductor element is mounted, forms the casing. Therefore, there is no need to provide a mount substrate within the casing in order to mount the semiconductor element. Accordingly, the semiconductor device can be made more compact by an amount corresponding to the lack of a mount substrate within the casing.
Moreover, a seventh aspect of the present invention is a semiconductor device including: (a) a cross substrate comprising at least one resin sealed layer of a cross member, the at least one resin sealed layer of a cross member having warp threads and weft threads, wherein a portion of at least one of the warp threads and weft threads include a plurality of conductive thread-like wire members disposed substantially parallel to one another, with the wire members electrically insulated from one another, and an electrode portion formed at one region of the thread-like wire members; (b) a heat-dissipating plate having a high heat transfer coefficient; and (c) a semiconductor element having a reverse surface side and a circuit forming surface side, the circuit forming surface side being mounted to the cross substrate, and the heat-dissipating plate being sealed at the reverse side surface. Even if heat is generated at the time the semiconductor device is operated, the heat can effectively be released to the exterior. Therefore, a semiconductor device can be obtained in which there is no fear of malfunctioning due to heat.
An eighth aspect of the present invention is a semiconductor device including: (a) a cross substrate comprising at least one resin sealed layer of a cross member, the at least one resin sealed layer of a cross member having warp threads and weft threads, wherein a portion of at least one of the warp threads and weft threads include a plurality of conductive thread-like wire members disposed substantially parallel to one another, with the wire members electrically insulated from one another, and an electrode portion formed at one region of the thread-like wire members; and (b) a semiconductor element having a reverse surface side and a circuit forming surface side, the circuit forming surface side being fixed to the cross substrate, and a conductive layer being disposed in a layer covering the reverse surface side. Mutual effects between semiconductor elements at the time the semiconductor device is switching-operated can be suppressed so that malfunctioning can be prevented. Thus, a semiconductor device which operates stably can be obtained.